Shortened rail glide head

ABSTRACT

A glide head using a slider with an outside active rail is described. In one embodiment, the trailing end of the outside rail extends beyond the trailing end of the inside rail. Thus, during use, the trailing end of the outside rail is closer to the surface of the magnetic disk because of the slope of the glide head&#39;s flight. Accordingly, the outside rail is the active rail. The inside rail may be wider than the outside rail to compensate for additional lift created by the greater length of the outside rail. In an alternative embodiment, the trailing end of the outside rail extends beyond the trailing end of the inside rail and there are notches located in the side edges of the rails. The notches do not extend to the forward tapered ends of the rails nor to the trailing ends of the rails. The notches provide additional stability during the slider&#39;s flight and decrease the air bearing area of the rails as needed for fly height requirements. In addition, the testing time is minimized by the wide trailing ends of the rails.

CROSS-REFERENCE TO PRIORITY APPLICATION

This application is a continuation of and claims priority from U.S.Patent application Ser. No. 08/831,878,filed Apr. 2, 1997, entitled“Glide Head With An Outside Rail” by Alexander A. Burga and Margelus A.Burga, now U.S. Pat. No. 5,963,396, which is incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to glide heads used to detect defects on thesurface of magnetic or magnetic-optical memory disks such as those usedin hard disk drives.

BACKGROUND OF THE INVENTION

A computer hard disk drive comprises a magnetic memory disk mounted on aspindle which is driven by a motor to rotate the magnetic disk at highspeed. A read/write head, kept in close proximity to the surface of therotating magnetic disk, reads or writes data on the magnetic disk. Theread/write head is separated from the surface of the magnetic disk by anair bearing created by the high speed rotation of the magnetic disk. Theread/write head flies on this air bearing, e.g., at a height ofapproximately one microinch. The closer the read/write head is to thesurface of the magnetic disk, the more information may be written on thedisk. Thus, it is desirable for the read/write head to fly as close aspossible to the surface of the magnetic disk.

Typical memory disks comprise a substrate that is plated with a hardmaterial such as a nickel phosphorus alloy. The nickel phosphorus isthen textured or roughened. An underlayer, a magnetic alloy ormagnetic-optical material, and a protective overcoat are then depositedon the nickel phosphorus, e.g., by sputtering. As mentioned above, thedisk manufacturing process leaves the surface of the disk in a slightlyroughened condition.

The precision with which the read/write head flies over the magneticdisk requires that care is taken during manufacturing to assure thatthere are no protrusions or asperities on the disk surface that mayinterfere with the read/write head. A protrusion on the surface of thedisk that contacts the read/write head during use may damage the head orthe disk.

Accordingly, during manufacturing of magnetic or magnetic-optical disks,tests are performed with “glide heads” to determine if there are anyasperities, voids or contamination that might interfere with theread/write head. Accurate testing of disks for such defects assures thatthe disk manufacturer does not unnecessarily reject good quality disksor pass on poor quality disks that may later fail.

During testing, the glide head must fly over the surface of the disk ata height no greater than the minimum fly height of the read/write head.FIG. 1 illustrates a glide head 1 flying over the surface of a magneticdisk 2. Disk 2 spins in the direction of arrow 3 about a spindle 4.Glide head 1 is connected to a suspension arm 5, which maintains theposition of glide head 1 relative to disk 2. Suspension arm 5 iscontrolled by an actuator 7, such as a stepper-motor actuator or avoice-coil actuator, which moves glide head 1 laterally over the surfaceof magnetic disk 2 in the direction of arrow 6. The lateral movement ofglide head 1 is slow relative to the high speed rotation of magneticdisk 2. Similar to a read/write head, glide head 1 flies over an airbearing that is created by the high speed rotation of magnetic disk 2.

FIG. 2 is a side view of magnetic disk 2 with a down facing glide head1A and an up facing glide head 1B flying over and testing surfaces 2Aand 2B of magnetic disk 2, respectively. Air bearings 8A, 8B, created bythe high speed rotation of magnetic disk 2, lie between glide heads 1Aand 1B and surfaces 2A and 2B, respectively. As in FIG. 1, glide heads1A and 1B are connected to suspension arms 5A, 5B. Arms 5A, 5B arecontrolled by actuator 7 to laterally move glide heads 1A, 1B oversurfaces 2A, 2B of magnetic disk 2 in the direction of arrow 6.

FIG. 3 shows glide head 1 flying over a section of magnetic disk 2rotating in the direction of arrow 3. The roughened texture of topsurface 2A of magnetic disk 2 is schematically shown in FIG. 3. FIG. 4Ashows a bottom surface of down facing glide head 1A. FIG. 4B shows atrailing side 15 of down facing glide head 1A. As shown in FIGS. 4A and4B, glide head 1A comprises a slider 9, a suspension arm 5 connected toa top surface of slider 9, and a transducer 10, such as a piezoelectriccrystal. (Transducer 10 and suspension arm 5 are schematicallyrepresented in FIG. 4B.) Slider 9 comprises an inside rail 11, anoutside rail 12, and a wing 13. Inside rail 11 and outside rail 12 bothhave forward tapered ends 14, which are tapered at an angle less thanone degree from horizontal (typically an angle between thirty minutesand fifty minutes). Tapered ends 14 provide lift to glide head 1A. Wing13 provides additional surface area to the top surface of slider 9 uponwhich transducer 10 is mounted. When rail 11 or 12 impact an asperity orcontamination on disk 2 or sink in response to encountering a void,transducer 10 converts the mechanical energy from the event into anelectrical signal which can be measured. Generally, however, inside rail11 generates a stronger signal output voltage when detecting a defectthan outside rail 12 when at the same fly height. Accordingly, it isdifficult to determine when outside rail 12 is detecting a defect. Also,when a signal is generated by transducer 10, it is difficult to know thesize of the defect that caused the signal, because one cannot knowwhether the signal was created by an encounter with the more sensitiveinside rail 11 or the less sensitive outside rail 12.

Because tapered ends 14 of inside rail 11 and outside rail 12 createlift, it is important that as slider 9 moves laterally across therotating surface of magnetic disk 2, both inside rail 11 and outsiderail 12 remain over the surface of magnetic disk 2. In other words, onecannot move slider 9 such that outside rail 12 extends past the outercircumference of disk 2. If outside rail 12 is moved beyond the outercircumference of disk 2, slider 9 will lose its lift under outside rail12 and will roll, causing slider 9 to contact magnetic disk 2.Accordingly, only outside rail 12 can detect asperities over theoutermost portion of the surface of magnetic disk 2. Obviously, thesurface of disk 2 adjacent the outer circumference must be tested forasperities. Thus, a glide head that can accurately test the outermostportion of the surface of a magnetic disk without losing its lift isneeded.

The distance that slider 9 may move laterally outward along the surfaceof magnetic disk 2 is determined by the width of rails 11 and 12. Inorder to cover the entire surface area on magnetic disk 2, slider 9 ismoved laterally, step by step, across the surface of magnetic disk 2.Each step must be at least slightly less than the width of one rail inorder to test the entire surface of the disk for defects. Accordingly,in order to minimize the time necessary to test each magnetic disk, aglide head with wide rails is desirable.

SUMMARY

A glide head in accordance with our invention uses the outside rail ofthe slider as the active testing rail. In addition, the rails of theslider are wide so that during testing the length of the steps that theslider is moved laterally over the surface of the magnetic disk can begreater, thereby minimizing testing time.

In one embodiment, the outside rail is longer than the inside rail sothat the trailing end of the outside rail extends beyond the trailingend of the inside rail and, thus, the outside rail is more sensitivethan the inside rail. The inside rail is wider than the outside rail tocompensate for the additional lift on the outside rail created by thegreater length of the air bearing surface of the outside rail. Bykeeping the area of the two rails approximately equal, the slidermaintains an equal amount of lift under both rails, thereby preventingthe slider from rolling during flight. In another embodiment, the areaof the rails is unequal and the location of contact with the suspensionarm may be moved to compensate for the increased lift created by thegreater area of the outside rail.

In another embodiment, each rail has a notch in the side facing theopposite rail. The notches, however, do not extend all the way to thetapered forward ends of the rails, nor to the trailing ends of therails. The notches stabilize the slider's flight. The notches also allowthe slider to retain wide tapered ends of the rails to provide lift andretain wide trailing ends to minimize testing time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates in plan view a glide head connected to a suspensionarm over a rotating magnetic disk in accordance with the prior art.

FIG. 2 is a side view of glide heads flying over both the top and bottomsurfaces of a magnetic disk in accordance with the prior art.

FIG. 3 is a perspective view of a glide head connected to a suspensionarm over the rotating magnetic disk in accordance with the prior art.

FIGS. 4A and 4B are bottom plan and end views, respectively, of a glidehead in accordance with prior art.

FIGS. 5A and 5B are bottom plan and end views, respectively, of a downfacing outside active rail glide head in accordance with the invention.

Figures 5A′ and 5B′ are bottom plan and end views, respectively, of anup facing outside active rail glide head in accordance with theinvention.

FIG. 6 is a side view of a slider connected to a suspension arm flyingover the surface of a magnetic disk.

FIG. 7 is a side view of an up facing outside active rail glide headwith an offset suspension arm.

FIG. 8 illustrates in plan view a glide head connected to a suspensionarm over the rotating surface of a magnetic disk.

FIGS. 9A and 9B are plan and end views, respectively, of an outsideactive rail glide head with notches in the rails.

FIGS. 10A, 10B and 10C are plan, end and side views, respectively, of anoutside active rail glide head with notches in the rails and connectedforward tapered ends.

FIG. 11 is a perspective view of an outside active rail glide head withdiscontinuities in both the inside rail and the outside rail.

DETAILED DESCRIPTION

FIGS. 5A, 5A′, 5B, and 5B′ illustrate 50% sliders with an outside activerail. The term “50%” is well known in the art, and refers to the size ofthe slider. FIG. 5A is a bottom plan view of a down facing slider 101and FIG. 5A′ is a bottom plan view of a corresponding up facing slider102. Figure 5B is an end view of a down facing slider 101 and FIG. 5B′is an end view of a corresponding up facing slider 102. For simplicity,only down facing slider 101, illustrated in FIGS. 5A and 5B, will bediscussed, but it should be understood that up facing slider 102 issimilar to down facing slider 101, but in mirror image, as illustratedin FIGS. 5A′ and 5B′.

As shown in FIGS. 5A and 5B, slider 101 has an inside rail 103 and anoutside rail 105. Both inside rail 103 and outside rail 105 have forwardtapered ends 104 and 106, respectively. Forward tapered ends 104 and 106have an angle of approximately sixty minutes from the horizontal.However, in other embodiments, other angles can be used, e.g., fromthirty minutes to one degree. Slider 101 is approximately 0.10 inches inwidth from its outside edge 110 to inside edge 111 (distance A in FIG.5A), 0.078 inches in length from its forward end 108 to trailing end 109(distance B), and 0.024 inches high from top surface 112 to the airbearing surfaces 113, 117 of the rails 103, 105 (distance C). It shouldbe understood, however, that all dimensions are merely by way ofexample, and the invention is not limited to a slider with thesedimensions. Other sizes may be used.

Slider 101 has an extension or wing 107 that extends slider 101 outwardfrom outside rail 105 approximately 0.040 inches (distance D), therebyincreasing the area of top surface 112 of slider 101. Wing 107 isapproximately 0.01 to 0.015 inches thick (i.e., distance E between topsurface 112 of slider 101 and bottom surface 114 of wing 107). As can beseen in FIG. 5A, outside rail 105 is longer than inside rail 103.Outside rail 105 traverses the entire length of slider 101 from forwardend 108 to trailing end 109 and is thus 0.078 inches long (distance B).Inside rail 103 extends to forward end 108, but is approximately 0.007inches short of trailing end 109 of slider 101 (distance F). Thus,trailing end 120 of outside active rail 105 extends approximately 0.007inches beyond trailing end 119 of inside rail 103. However, in otherembodiments, outside active rail 105 extends beyond trailing end 119 ofinside rail 103 by other distances, e.g., by a distance between 1% to50% of the length of outside rail 105. In another embodiment, taperedforward end 104 of inside rail 103 may not extend to forward end 108 ofslider 101, such that tapered forward end 106 of outside rail 105extends some distance, e.g., approximately 0.007 inches, in front oftapered forward end 104 of inside rail 103.

As shown in FIG. 6, as slider 101 flies over surface 121 of the rotatingmagnetic disk 122 at a slope angle θ, which generally is approximately0.015 degrees or less. Because slider 101 flies with a slope angle,trailing ends 119 and 120 of the rails are the closest part of slider101 to surface 121. Accordingly, trailing ends 119 and 120 are the areason rails 103 and 105 that are most sensitive to defects on surface 121.Because trailing end 120 of outside rail 105 extends beyond trailing end119 of inside rail 103 (shown in phantom in FIG. 6), outside rail 105 iscloser to surface 121 of the disk. Thus, outside rail 105 (is moresensitive) than inside rail 103, making outside rail 105 the active railand inside rail 103 the non-active rail.

Inside non-active rail 103, however, is wider than outside active rail105 to compensate for the increased lift caused by the greater length ofoutside active rail 105. The wide inside rail 103 prevents slider 101from rolling during flight. The width of rails 103 and 105 depends onthe fly height requirements and the rotational velocity of magnetic disk122. By way of example, with slider 101 flying at one microinch at aslope of 0.03 degrees over magnetic disk 122, and disk 122 rotatingbeneath slider 101 such that the portion of disk 122 under slider 101travels at 500 inches per second, inside non-active rail 103 may beapproximately 0.015 inches wide (distance G) and outside active rail 105may be approximately 0.012 inches wide (distance H). The distancebetween the outside edge of outside active rail 105 and the inside edgeof inside non-active rail 103 is approximately 0.058 inches (distanceI). The inside non-active rail 103 is set in from the inside edge 111 ofslider 101 approximately 0.002 inches. The distance between top surface112 of slider 101 and bottom surface 115 between rails 103 and 105 isapproximately 0.02 inches (distance K).

Slider 101 is machined using standard machining methods out of a waferof aluminum oxide-titanium carbide such as material type no. 310,available from 3M Corporation located in Minnesota. Notches 130 and 131in bottom surface 115 of slider 101, as shown in Figure 5B are createdduring the machining process.

Suspension arm 116 (FIG. 5B and FIG. 6) is connected to top surface 112of slider 101 and provides a gram force on slider 101 toward surface112. A typical gram force can be approximately 2, 3.5, 6, 9.5, or 15grams. In an alternate embodiment, the width of inside rail 103 is notincreased to compensate for the greater lift of outside rail 105.Instead, as illustrated in FIG. 7, suspension arm 116′ may be offset ontop surface 112 of slider 101 from the previous embodiment's locationfor suspension arm 116 (shown in phantom). Offsetting suspension arm116′ prevents roll induced by the additional lift generated from outsiderail 105, which is longer than inside rail 103. Thus, in thisembodiment, inside rail 103 may have the same width as outside rail 105.An appropriate suspension system arm is a type 2, 4, 13, 18.50 or 19model available from Magnecom, Inc. of San Diego. A piezoelectriccrystal (PZT) 118 (FIG. 5B and FIG. 7) is mounted to top surface 112 ofwing portion 107 of slider 101. An appropriate PZT crystal should be ofgood quality such as is available from Secor, Ltd. located in the UnitedKingdom.

FIG. 8 illustrates an assembled glide head 123 mounted on a suspensionarm 116 and over a magnetic disk 122 to be tested. Disk 122 has alanding zone 125 adjacent an inner perimeter of surface 121, near aspindle 124. A data zone 126, where data is stored on magnetic disk 122,is outward from landing zone 125 on surface 121. When magnetic disk 122is not rotating there is no air bearing generated over surface 121 andglide head 123 rests on surface 121 in landing zone 125. As magneticdisk 122 begins rotation as indicated by arrow 127, an air bearing isgenerated over surface 121 and lift is provided to glide head 123 by theair bearing. A typical rotational velocity of disk 122 produces a linearvelocity of 300 to 500 inches per second beneath glide head 123 duringtesting. Glide head 123 first tests the landing zone for defects.Magnetic disk 122 rotates at high speed creating a high fly height forglide head 123 during testing of landing zone 125. A concentric circlein the landing zone 125 is tested by glide head 123. An actuator 128moves glide head 123 laterally across data zone 125 as indicated byarrow 129 so that another concentric circle in landing zone 125 may betested. When glide head 123 has completed testing landing zone 125 fordefects, actuator 128 continues to move glide head 123 laterally acrosssurface 121 into data zone 126. The rotation of magnetic disk 122 isthen slowed so that glide head will have a lower fly height,approximately one microinch, during testing of the data zone 126.Actuator 128 continues to move glide head 123 across data zone 126 untilthe entire area of surface 121 has been tested. Actuator 128 moves glidehead 123 laterally across surface 121 by a distance less than the widthof outside rail 105. In this manner glide head 123 tests, step by step,the entire area of surface 121 for defects.

Another embodiment of a slider is shown in FIGS. 9A and 9B. FIGS. 9A and9B show an ion milled 50% slider with an outside active rail. The 50%slider is illustrated as an example, and any size slider may be made inaccordance with this embodiment. The slider body in this embodiment maybe manufactured by conventional ion milling. FIG. 9A is a bottom planview of a down facing 50% slider 151. FIG. 9B is an end view of downfacing slider 151. For the sake of simplicity, only down facing slider151 will be discussed, but it should be understood that a correspondingup facing slider is similar to down facing slider 151, but in mirrorimage.

In this embodiment, the overall dimensions of slider 151 are similar tothe dimensions of slider 101 in FIGS. 5A and 5B. Because slider 151 ision milled, however, inside non-active rail 153 and outside active rail155 are only raised approximately 0.0002 inches from a bottom surface163 (FIG. 9B) of slider 151 (distance M). Accordingly, only minimalmaterial is removed from slider 151 and wing 157, which extends slider151 outward from outside active rail 155. Thus, slider 151 and wing 157are thicker than slider 101 and wing 107 (Figures 5A and 5B) of theprevious embodiment. The distance between top surface 162 of slider 151and bottom surface 163 of slider 151 between the two rails 153 and 155is the same distance from top surface 162 of slider 151 and bottomsurface 164 of wing 157, approximately 0.035 inches (distance N). Theadditional thickness in slider 151 and wing 157 increases the overallstiffness. The additional stiffness increases the signal strength of PZTcrystal 169, and causes a higher frequency output thereby improving thedetection of small defects.

Outside rail 155 is longer than inside non-active rail 153. Trailing end168 of outside rail 155 extends beyond trailing end 167 of inside rail,again making outside rail 155 the active rail. In addition, asillustrated in FIG. 9A, forward tapered end 156 of outside rail extendsbeyond forward tapered end 154 of inside rail 153. In this embodiment,the sides of outside active rail 155 and inside non-active rail 153 havenotches. Outside active rail 155 has a “V ” shaped notch 166 on theinside edge. Inside non-active rail 153 has a “U” shaped notch 165 onthe outside edge. Notches 165 and 166, however, do not extend to taperedends 154 and 156, nor to trailing ends 167 and 168. These notches 165and 166 stabilize slider 151 during flight, preventing slider 151 fromrolling. Notches 165 and 166 decrease the area of rails 153 and 155 asneeded for fly height requirements, while still providing the sameamount of lift from tapered forward ends 154 and 156. Notches 165 and166 do not extend to trailing ends 167 and 168 permitting trailing ends167 and 168 to remain wide. Because slider 151 is moved laterally acrossthe surface of the magnetic disk in steps equal to the width of trailingend 168 of outside rail 155, keeping trailing end 168 wide minimizestesting time. In this embodiment, notches 165 and 166 are formed duringthe conventional ion milling process. However, it is understood thatthese notches can be formed using other methods, such as conventionalmachining. It is further understood that notches 165 and 166 may haveshapes other than as described above.

FIGS. 10A, 10B and 10C illustrate another embodiment of a slider inaccordance with the present invention. FIGS. 10A, 10B and 10C show a 50%slider. The 50% slider is illustrated as an example, and any size slidermay be made in accordance with this embodiment. The slider body in thisembodiment may be manufactured by conventional ion milling. FIG. 10A isa bottom plan view of a down facing 50% slider 170. FIG. 10B is an endview of down facing slider 170 and FIG. 10C is a side view of downfacing slider 170. For the sake of simplicity, only down facing slider170 will be discussed, but it should be understood that a correspondingup facing slider is similar to down facing slider 170, but in mirrorimage.

This embodiment has approximately the same dimensions as the embodimentshown in FIGS. 9A and 9B. As with slider 151, because slider 170 is ionmilled inside rail 171 and outside rail 172 are only raisedapproximately 0.0002 inches from a bottom surface 176 (Figure 10B) ofslider 170 (distance M). Further, the distance between top surface 177of slider 170 and bottom surface 176 of slider 170 between rails 171 and172 is the same distance from top surface 177 and bottom surface 176 ofwing 178, approximately 0.035 inches (distance N). As in slider 151,slider 170 has notches 179 and 180 in the sides of rails 171 and 172.

Trailing end 174 of outside rail 172 extends beyond trailing end 173 ofinside non-active rail 171, again making outside rail 172 the activerail. In this embodiment, however, the forward end of inside rail 171extends as far forward as the forward end of outside rail 172 and theforward ends of inside rail 171 and outside rail 172 are connected suchthat there is one forward end 175 that connects outside rail 172 withinside rail 171. Forward end 175 serves to increase stability of slider170 in flight. Forward end 175 has a step type taper of approximately0.0001 inches (distance O), as illustrated in FIG. 10C. In anotherembodiment, forward end 175 may have a beveled taper with an anglebetween thirty minutes to one degree.

Although the present invention is illustrated in connection withspecific embodiments for instructional purposes, the present inventionis not limited thereto. Various adaptations and modifications may bemade without departing from the scope of the invention. For example, theslider material is not limited to aluminum oxide-titanium carbide. Theslider surface may be coated with carbide by sputtering or other similartechniques to increase the durability of the slider. Different sizes anddimensions of the slider may be used. Different types of suspensions,and transducers other than piezoelectric crystals may be used. Also asshown in FIG. 11, inside rail 183 and outside active rail 185 need notbe continuous and may have gaps or other discontinuities in them. Inlieu of providing tapers, one can provide steps in the forward ends ofthe rails. Accordingly, all such changes came within our invention.

What is claimed is:
 1. A glide head to detect defects on a disksubstrate, said glide head having a leading end, a trailing end, and anair bearing surface, said glide head comprising: a first rail extendingdownwardly from said air bearing surface, said first rail having aleading end located toward said leading end of said glide head and atrailing end located toward said trailing end of said glide head; asecond rail extending downwardly from said air bearing surface, saidsecond rail having a leading end located toward said leading end of saidglide head and a trailing end located toward said trailing end of saidglide head, said trailing end of said second rail extending further inthe direction of said trailing end of said glide head than said trailingend of said first rail, wherein said second rail generates a greateramount of mechanical energy from encountering a defect than said firstrail; and a transducer mounted on said glide head, said transducersensing when said glide head encounters a defect, said transducerconverting said mechanical energy from encountering said defect into anelectrical signal.
 2. The apparatus of claim 1, wherein said transducermounted on said glide head is a piezoelectric crystal mounted on saidtop surface of said glide head.
 3. The glide head of claim 1, whereinsaid first rail has an inside edge and an outside edge, and said secondrail has an inside edge and an outside edge, wherein the distancebetween said inside edge and outside edge of said first rail is greaterthan the distance between said inside edge and said outside edge of saidsecond rail.
 4. The apparatus of claim 1, wherein said glide headincludes a wing outwardly extending said top surface of said glide headfrom one of said first rails or second rails, said transducer beingmounted on said wing.